Cellular immunity against a large variety of human tumors has now been demonstrated with the Colony Inhibition assay of I. Hellstrom. In some patients tumor specific cytotoxic humoral antibodies have been found; in others a serum blocking factor is present which abrogates the cytotoxic effects of their immunocytes. The aim of this clinical research program is to correlate in vitro assays of tumor specific cellular and humoral immunity with several important pathological and clinical factors; i.e., the histologic type and degree of differentiation of the tumor, the presence or absence of vascular and lymphatic invasion, the presence or absence of regional and/or distant metastases, and to determine in what way changes, if any, in the patient's tumor-specific immune status correlate with the natural course of his disease (survival time, time between diagnosis and appearance of metastases and recurrence) and if, and in what way, his immune status is altered by conventional modes of therapy. It is anticipated that data gained from this kind of study will permit more effective use of current treatments and may provide clues as to the best approach for human cancer immunotherapy.